Tire shredding machines are used to reduce tires, particularly automotive tires, to small pieces of rubber which can be reused in manufacturing a variety of products. With reference to FIG. 1, a typical tire reduction system of the prior art is seen, as described in U.S. Pat. No. 6,343,755 to Barclay and Diemunsch. A continuous feed of tires 15, is placed on conveyor belt 10 for motion toward the primary rotary shearing assembly 11. A toothed feeder wheel 13 seizes tires from the conveyor belt and pushes them into the primary shearing assembly 11 for digestion. The primary shearing assembly, relying on the rotary shears 17 and 19, reduces full tires to several 42 inch strips 21, depending on the number of rotary shears, each of which is typically 6 inches wide at the shearing blade, such that at least 6 shearing wheels plus spacers would be needed to span the diameter of an average tire. A second conveyor belt 20 moves the tires to secondary shearing assembly 23. Here, a pair of secondary rotary shears 26 and 28, mounted within box 27, held by support rails 29, receives the various length strips from bin 25. The secondary shearing assembly 23 reduces the pieces 32, falling onto conveyor belt 30, typically ranging in size between 1.5 inches and 4 inches. Electric motor 31 provides the force for driving the primary and secondary shears simultaneously in tandem.
In FIG. 2, detailed operation of primary shearing wheels of a rotary shearing assembly of FIG. 1 is seen. A first shearing wheel 17 is shown meshing with a second shearing wheel 19. Each shearing wheel is mounted on a drive shaft and has shearing members 33 mounted adjacent to an annular non-unitary spacer 35, separating the cutter assembly from an adjacent cutter assembly. The annular spacer may be segmented and is driven by a drive shaft or hub by key members 37. Bolts joining the annular spacer to the cutter assembly allow the shearing members to be individually removed from each shearing wheel for resharpening, following the teachings of U.S. Pat. No. 4,901,929 to R. Barclay. First and second sets of shearing assemblies mounted on respective shafts in interleaving relationship act as rotary shears for tires fed between the assemblies in the direction of arrow A. The stripper rolls 41 and 43 clear the spaces between spaced apart shearing members of each shearing wheel 17 and 19. Arcuate steel segments 45 and 47 in each roll are side mounted to a separate annular member 49 for ease of maintenance as described in U.S. Pat. No. 4,776,249 to R. Barclay.
With reference to FIG. 3, a rotary shear 51, described in U.S. patent application Ser. No. 10/185,500, filed Jun. 27, 2002, of a primary shredder is shown to have a cutting wheel with cutting assemblies 53 and 55 mounted on a hub 63 having a central longitudinal axis 57 with which the cutting wheels are concentric. Hub 63 rotates about axis 57. Between the cutting assemblies is a core 61 which serves as a spacer between cutting assemblies 53 and 55. The periphery of the spacer is smooth and is slightly recessed compared to the periphery of the cutting wheels. The cutting assemblies have a serrated circumferential profile which arises from segments 71 which are pie-piece shaped, except that the segments slightly overlap each other, creating a serrated profile. Each segment has a base 77 with a blade 79 atop the base and circumferentially aligned with the base by means of a linear keyplate 74, running the length of base 77 and blade 79, encapsulated between the base 77 and the blade 79. By aligning the base 77 and blade 79, the keyplate 74 allows a blade to be used on two side and also serves to keep blades from sliding. Radially extending bolts 81 hold the blade 79 to base 77 while axial bolts 83 hold the pie-piece segment to the core 61. An end plate 80 may be seen at one end of hub 63. Although not shown, the end plate is preferably equipped with peripheral blades for engaging an adjacent shearing wheel in a shearing relationship. All axial bolts are secured to the end plate. There are sufficient rotary shears on each hub to span the width of a tire.
Part of the maintenance routine for a tire shredding machine requires replacing worn blades on the cutting wheels. This needs to be done as quickly as possible so that the machinery can resume operation. In addition, discrete pieces of the blades (the base of the blade, the cutting blade, etc.) may require replacement while the rest of the blade is still usable. Modular blade assemblies, similar to those discussed in FIG. 3, above, which have base and blade components which are fastened together, are used to enable quick and efficient repair.
The keyplate of the modular blade assembly is made of softer metal than the base or blade. This could potentially weaken the modular blade assembly since the keyplate described in FIG. 3 extends the width of the top of the base and the bottom of the blade and therefore is subject to stresses which could damage the keyplate, requiring it to be replaced. It would be advantageous to have a modular blade assembly which is less susceptible to damage and easy to manufacture.